I'm familiarizing myself with the Buddha's first discourse, and I was hoping for some information about its Pali commentaries and sub-commentaries. I don't necessarily think I'll be able to find translations...but who knows? Thanks in advance!

Here are some notes from Bhikkhu Bodhi's translation of the Samyutta Nikaya. The translation itself is here: http://suttacentral.net/sn56.11/en/ but the footnotes are omitted.

You'll see from these notes that the Visuddhimagga,(available online - see below) contains a very detailed commentary.

Bhikkhu Bodhi wrote:What follows is the Buddha’s first sermon, recorded in the narration of his ministry at Vin I 10-12. The sutta is analysed at MN No. 141 and Vibh 99-105, and commented upon at Vism 498-510 (Ppn 16:32-83) and Vibh-a 93-122. For a detailed explanation according to the method of the commentaries, see Rewata Dhamma, The First Discourse of the Buddha.

[THE TRUTH OF SUFFERING][(I) BIRTH]32. Now, this word birth (játi) has many meanings. For in the passage “[Herecollects ... ] one birth (játi), two births” (D I 81) it is becoming. In the passage,“Visákhá, there is a kind (játi) of ascetics called Nigaóþhas (Jains)” (A I 206) it isa monastic order. In the passage, “Birth (játi) is included in two aggregates”(Dhátuk 15) it is the characteristic of whatever is formed. In the passage, “Hisbirth is due to the first consciousness arisen, the first cognition manifested, inthe mother’s womb” (Vin I 93) it is rebirth-linking. [499] In the passage “Assoon as he was born (sampatijáta), Ánanda, the Bodhisatta ...” (M III 123) it isparturition. In the passage “One who is not rejected and despised on account ofbirth” (A III 152) it is clan. In the passage “Sister, since I was born with the noblebirth” (M II 103) it is the Noble One’s virtue....[goes for 50 paragraphs...]

Rewata Dhamma, The First Discourse of the Buddha, appears to be out of print.

“So long, bhikkhus, as my knowledge and vision of these Four Noble Truths as they really are in their three phases and twelve aspects was not thoroughly purified in this way,...

The three phases (tiparivaṭṭa) are: (i) the knowledge of each truth (saccañāṇa), e.g., “This is the noble truth of suffering”; (ii) the knowledge of the task to be accomplished regarding each truth (kiccañāṇa), e.g., “This noble truth of suffering is to be fully understood”; and (iii) the knowledge of accomplishment regarding each truth (katañāṇa), e.g., “This noble truth of suffering has been fully understood.” The twelve modes (dvādasākāra) are obtained by applying the three phases to the four truths.

And when the Wheel of the Dhamma had been set in motion by the Blessed One, ...

Spk explains dhammacakka by way of the knowledge of penetration (paṭivedhañāṇa) and the knowledge of teaching (desanāñāṇa); See II, n. 57:

Spk glosses brahma as seṭṭha, uttama, “the best, the highest,” and explains the Brahma-wheel as the purified Wheel of the Dhamma (visuddhadhammacakka). This is twofold, the knowledge of penetration (paṭivedhañāṇa) and the knowledge of teaching (desanāñāṇa). The former originates from wisdom and brings the Buddha’s own attainment of the noble fruits; the latter originates from compassion and enables him to teach in such a way that his disciples attain the fruits. The knowledge of penetration is supramundane (lokuttara), the knowledge of teaching mundane (lokiya). Both are self-begotten types of knowledge belonging exclusively to the Buddhas, not held in common with others.

Until Koṇḍañña and the eighteen koṭis of brahmās were established in the fruit of stream-entry the Blessed One was still setting in motion (pavatteti nāma) the Wheel of the Dhamma; but when they were established in the fruit, then the Wheel had been set in motion (pavattitaṃ nāma).